WASHINGTON (AP) -- Attorney General Eric Holder says four American citizens have been killed in drone strikes since 2009.

The attorney general said that in conducting U.S. counterterrorism operations against al-Qaida and its associated forces, the government has targeted and killed one American citizen, Anwar al-Awlaki.

In a letter to Senate Judiciary Committee Chairman Patrick Leahy, Holder says the U.S. is also aware of three other American citizens who have been killed in such counterterrorism operations over the same time period.